A recent semiconductor device is mounted with a CPU (Central Processing Unit) and a memory, and further has an analog-to-digital (A/D) conversion function. Such semiconductor devices are often handled as product groups serialized based on a memory capacity, the number of A/D conversion channels, the number of I/O (input/output) channels, an operation speed, and so on. Moreover, even for similar functions, the semiconductor devices may be sealed in different packages. While a degree of freedom for mounting increases, functional limits may be imposed due to limits imposed on the number of pins depending on different packages.
For example, in a continuous scan operation of an A/D conversion apparatus, an A/D conversion is sequentially performed while analog input channels are counted and switched. When a semiconductor chip has analog input pads arranged continuously, even though the semiconductor chip is optimal to be mounted in a package having the maximum number of pins, it is not necessarily optimal that the semiconductor chip is mounted in a package having the small number of pins. Therefore, in order to design such a semiconductor device to be mounted in different packages, arrangement of input pins should be considered to be adaptive for each of the packages. In the worst case, the continuous scan must be performed by use of discontinuous channel numbers. In this case, a large load is imposed on development of a control program.
At this point, even if input pads and input pins are connected by bonding wires so that channel numbers become continuous, assembly failure is highly likely to occur. To avoid this, it could be considered that the analog input pads located close to the input pins of the package are selected as analog input channels to be scanned. However, there is a case that connectable analog input channels cannot be continuously provided, depending on positions of the input pins of the package. In such a case, the analog input channels provided in the package must take discrete channel numbers inevitably. When valid analog input channels take discrete channel numbers, processing of a program in which a scan operation is performed for the A/D conversion becomes complicated as described above. Also, the software could not be used for a different series of products.
Moreover, a lead frame is required to have a special shape to adapt for the shape of the semiconductor chip, which leads to a cost increase.
Japanese Patent Publication (JP 2005-303575A) describes an A/D conversion apparatus which can continuously perform A/D conversion without stop. The A/D conversion apparatus includes a register, a selecting section connected to a plurality of analog input channels to which a plurality of analog signals are supplied, and an A/D converting section. The register holds channel specification data to indicate whether or not each of the plurality of analog signals should be subjected to A/D conversion. The selecting section sequentially selects the analog input channels to be subjected to the A/D conversion based on the channel specification data. The A/D converting section performs A/D conversion on the analog signals on the analog input channels selected by the selecting section, to convert them into digital signals. Consequently, the analog signals with different A/D conversion periods can be converted into the digital signals in appropriate conversion periods. Thus, load of software development for control of the A/D conversion and processing of the conversion results can be reduced.
Moreover, Japanese Patent Publication (JP-A-Heisei 9-297658) discloses an A/D conversion apparatus including a channel selector, an A/D converting section, and a control section. The channel selector selects a plurality of analog signal input terminals, and the A/D converting section converts analog signals supplied from the terminals selected by the channel selector into digital signals. The A/D conversion apparatus has a scan mode at the time of reception of a scan conversion start trigger, and a single mode at the time of reception of a single conversion start trigger, and the control section controls the channel selector to set one of the scan mode and the single mode with priority.